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Axle bearing problem 2

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tienti

Mechanical
May 1, 2012
27
Hello,

I have this axle part of a wheel assembly and need some basic hand calculations done on the axle. I attached a outline of the picture of the problem. I was thinking of treating this like a round bar and calculating the max deflection and comparing that with a computer simulation. How would i calculate the von mises stress on this cylindrical piece?

Doing Work
 
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Von Mises is the triaxial state of stress with shear rotated to the principle plane. So compute the shear, bending, rotation and deflections using a loaded circular beam of specified length. A wheel on an axial is basically a cantilever subjected to some load intensity since force is distributed along the width of the wheel.

You can find examples of this in elementary statics textbooks, first year engineering. Work through a problem that closely resembles yours. No big magic here.

Regards,
Cockroach
 
i wouldn't calc von Mises for this.

can you calc the moment in the axle ? (it is pretty simple)

can you calc a bending stress ? (likewise pretty basic)

compare this to max normal stress in your model. (just because the model tells you vM stress doesn't mean that's the only thing to compare with)

to calc vM stress you need to calc the three principal stresses.
 
Tienti:
What is a von mises stress, anyway? That certainly is a basic (meaningless) sketch for an engineering problem, which appears not to be very well understood. Why don’t you just get three different FEA softwares and a few cads, and model that axle several different ways in each software; then average the colors in the various outputs for your results, and call it good. That kind of averaging is called a ‘von mouses stress’ and saves all the hard work of hand calculations and any need to understand what you are doing from the technical and engineering standpoint. You will need a color-o-metrication digitizer to do this averaging, but it’s worth it. Did anyone even know who Von Mises was before FEA software started spitting out Von Mises stresses, or how stressed out he really was all these years? As mentioned above, get out some first year Statics and Strength of Materials text books and start actually formulating a meaningful problem and questions and come back with something we can actually discuss.
 
Attached would be a solution that you would be interested with.

Regards,
Cockroach
 
Attached would be the solution you would be interested with.

Regards,
Cockroach
 
Awesome Cockroach!

I just did a similar method to this except with just a point load in between the two bearings. I shall look over your calcs, I know need to review my basic statics, too much time spent away Thank you.
 
You can do it like that also, Tienti. A diss tributes load can be substituted as a point load provided the line of action is at the centroid of the distribution. This is one way to get reactions on a beam, for example.

I simply used the distributed load because it showed a better shear and bending moment diagram for such a small axle.

Regards,
Cockroach
 
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